In recent years there has been a flurry of activity among astronomers who are discovering more and more exoplanets. Over 200 have thus far been found, and most of these are gas giants. The reason for this is because gas giants, being very large, exert a greater gravitational pull. The most successful technique for finding exoplanets has been to observe how stars move; observatories such as the Hubble Telescope are sensitive enough to detect if a star has a slight wobble to it, which indicates the presence of planets and a solar system. Combining this method with infrared spectroscopy, it is possible to detect the molecular composition of distant planets. Carbon dioxide and monoxide, hydrogen, neon gas, water, and hydrocarbons have all been detected. Astronomers are quite confident that they are seeing planets outside our solar system that have atmospheres, and they speculate that some may have life-supporting liquids and gasses.